Adventhöhle Breitscheid, Show cave in Breitscheid, Germany.

The Herbstlabyrinth-Adventhöhle-System near Breitscheid is Hesse's largest cave system, surveyed at 13,183 metres in March 2025 with a depth of 92 metres. Its show cave section, the Knöpfchenhalle, is 80 metres long and up to 32 metres high, reached by a 45-metre tunnel with 125 steps. The cave is known for its clean white to transparent flowstone, including an eight-metre-long, 50-centimetre-wide sinter flag and numerous excentriques.

The Adventhöhle section was discovered by cave explorers in December 1993, with the Herbstlabyrinth section found months later. The two sections connected in 1995, forming the unified system visitors explore today.

The cave serves as a learning space within the National Geopark Westerwald-Lahn-Taunus, where visitors experience underground limestone landscapes firsthand. People come here to understand how water shapes stone over millennia and creates hidden underground worlds.

The cave is open from April through October on weekends and holidays, and exploration is only possible with guided tours. Groups are limited to 13 visitors per tour to keep the underground experience comfortable and safe.

The show cave's Knöpfchenhalle, 80 metres long and up to 32 metres high, was chosen because nearly every dripstone type found in the cave occurs there. Among its formations are several massive sinter organs and a sinter flag about eight metres long and 50 centimetres wide. Visitors reach it through a 45-metre tunnel with a staircase of 125 steps.